This document describes a mixed-element approach to perform mixed-mode crack propagation calculations in an arbitrary structure in a fully automatic way. In a preprocessing step a cylindrical volume about the crack front is meshed with hexahedral elements while the remaining parts of the structure at interest are filled with tetrahedrons. Subsequently, a finite element calculation is performed yielding the stress field at the crack tip. The postprocessor determines the stress intensity factors and the 3-dimensional crack growth, leading to a new crack front. This procedure is repeated until a user-defined criterion is reached. The method is illustrated by an aircraft casing component.